• Control of threadleaf rubber rabbitbrush with herbicides

      Whisenant, S. G. (Society for Range Management, 1988-11-01)
      Foliar sprays of 2,4-D [(2,4-dichlorophenoxy)acetic acid]), picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid), dicamba (3,6-dichloro-2-methoxy benzoic acid), or clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were applied in 30 or 150 L of total spray solution ha-1 to threadleaf rubber rabbitbrush [Chrysothamnus nauseosus ssp. consimilis (Greene) Hall & Clem] in Garfield County, Utah. Additional herbicide treatments were applied in 150 L ha-1 in Sevier County, Utah. Herbicides were less effective when applied in 30 L ha-1 than when applied in 150 L of total spray solution ha-1. Mortality was 74 to 87% following applications of 4.4 kg a.e. (acid equivalent) 2,4-D ha-1. Dicamba applied at 3.3 kg ha-1 resulted in 70 to 87% mortality, and picloram applied at 0.8 kg ha-1 resulted in 56 to 79% mortality. The greatest mortalities (84 to 97%) occurred on areas treated with 2.2 kg clopyralid ha-1. Mortality of threadleaf rubber rabbitbrush increased an average of 28, 17, 33, and 27% following applications of 2,4-D, dicamba, picloram, and clopyralid respectively, by using 150 L spray volume. Greatest increases were at the lowest herbicide rates. Applying herbicides in greater amounts of carrier (water) significantly increased both mortality and canopy reduction of threadleaf rubber rabbitbrush for at least 39 months.
    • Defoliation of Thurber needlegrass: herbage and root responses

      Ganskopp, D. (Society for Range Management, 1988-11-01)
      Thurber needlegrass (Stipa thurberiana Piper) is an important component of both forested and shrub-steppe communities of the Pacific Northwest and Great Basin regions, and little is known of its tolerance to defoliation. A study was conducted on the Squaw Butte Experimental Range to determine the response of containerized Thurber needlegrass to single defoliations (2.5-cm stubble) throughout the growing season. Dates of treatment spanned vegetative through quiescent stages of phenology. Response variables included: summer regrowth, number of reproductive stems, fall growth, and subsequent spring herbage production, change in basal area, and root mass. Vigor of Thurber needlegrass was reduced most by defoliation during the early-boot stage of development. Impacts were successively less severe from vegetative, late-boot, and anthesis treatments, respectively. Cumulative herbage production the year of treatment was reduced from 38 to 64% by defoliation at the early-boot stage. The same treatment reduced subsequent spring growth by 46 to 51% and root mass the next spring by 34 to 45%. Treatment effects were somewhat reduced when temperature and moisture regimes allowed substantial regrowth after defoliation. Defoliation during or after anthesis had little effect on plant response. Managers should be aware that a single defoliation, particularly during the boot stage, can significantly reduce subsequent herbage production and root mass and possibly lower the competitive ability of Thurber needlegrass.
    • Effects of dormant-season herbage removal on Flint Hills rangeland

      Auen, L. M.; Owensby, C. E. (Society for Range Management, 1988-11-01)
      Stocking rate effects on intensive-early stocked Kansas Flint Hills range were studied from 1982 through 1987. Rates were 2X, 2.5X, and 3X normal season-long stocking rates for 200-225 kg steers. Study design was a randomized complete block with 2 replicates. Grass and forb standing crop (kg/ha) were estimated at the time of livestock removal (mid July) and again in early October. Plant basal cover and composition were taken in early June the year prior to the study and annually thereafter. Overall growing season precipitation during the study period was below normal, with late-summer precipitation much below normal in the second and third years of the study. Grass standing crop (GSC) in mid July decreased with increased stocking rate, but by early October GSC was similar under the 2.5X and 3X stocking rates, but continued to be lower than that under the 2X rate. There was no consistent response in mid July forb standing crop (FSC) with respect to stocking rate. In early October, FSC was either not affected by stocking rate (1983, 1986, and 1987) or was greater under the highest stocking rate (1982, 1984, and 1985). The major changes in botanical composition and basal cover were a reduction in Indiangrass (Sorghastrum nutans Nash) and an increase in Kentucky bluegrass (Poa pratensis L.) as stocking rate increased. Botanical composition of big bluestem (Andropogon gerardii Vitman) increased under the 2X rate but did not change under the higher rates. Individual steer gains were similar under the different stocking rates, but livestock breed appeared to affect magnitude of the gain. Since individual gains did not differ, gains per ha were substantially increased by the higher stocking rates.
    • Effects of phenology, site, and rumen fill on tall larkspur consumption by cattle

      Pfister, J. A.; Manners, G. D.; Ralphs, M. H.; Hong, Z. X.; Lane, M. A. (Society for Range Management, 1988-11-01)
      Tall larkspur (Delphinium barbeyi) is a major cause of livestock death on mountain ranges. The influence of plant phenology, grazing site, and rumen fill on tall larkspur consumption was evaluated during July and August, 1987. Livestock consumption of larkspur was determined using bite counts during 4 phenological stages: bud, early flower, flower, and pod. Further, we examined larkspur ingestion in a shaded tree site and in an open sun site at 0, 50, and 100% rumen fill levels using ruminally cannulated steers. Steers on the 0, 50, and 100% fill levels consumed 9, 15, and 17% larkspur, respectively (P=0.15). There was a site effect (P=0.06) with steers eating 17 and 11% larkspur in the shade and sun sites, respectively. Over the summer, larkspur comprised 6% of cattle diets. No larkspur was consumed during the bud stage. Larkspur consumption peaked at 10% of cattle diets during the pod stage. Leaves of tall larkspur contained >3% total alkaloids (dry weight) in early July, but declined greatly with maturation. Larkspur was very nutritious, with crude protein levels 12 to 20%, and fiber levels <20% during most of the summer. Cattle diets, as determined with esophageally fistulated animals, were also high in crude protein and low in fiber during the summer. We propose a toxic window hypothesis relating larkspur palatability and toxicity. This hypothesis predicts that most cattle losses will occur during the flowering stage. We found that tall larkspur was unpalatable to cattle from the bud stage until the flowering racemes had elongated, and then consumption generally increased with plant maturation. Even though palatability and consumption increase during the grazing season, cattle can graze tall larkspur with a much lower risk of toxicosis when toxicity is low later in the grazing season.
    • Habitat selection and activity patterns of female mule deer in the Front Range, Colorado

      Kufeld, R. C.; Bowden, D. C.; Schrupp, D. L. (Society for Range Management, 1988-11-01)
      Twenty-two adult, female mule deer (Odocoileus hemionus hemionus) were radio-collared with activity sensors and monitored with ground triangulation from mid-November through March, for 3 years (1982-1985) in the foothills west of Fort Collins, Colorado, to test 4 general hypotheses about habitat selection and activity: (1) The proportion of time deer spend feeding and resting varies with time of day. (2) Deer alter their activity patterns in response to environmental influences. (3) Selection of specific vegetation types for feeding and resting varies with time of day. (4) Ecotones are preferred habitats. Deer were monitored during 6-hr sampling periods: sunrise, daytime, sunset, and night. Deer fed most during sunset, night, and sunrise periods and least during the day. Feeding occupied similar proportions of an average deer's time during sunset, night, and sunrise periods. They preferred the grassland type for feeding and resting at night and the mountain mahogany (Cercocarpus montanus) type for both activities during all other periods. Preference deer showed for the ponderosa pine (Pinus ponderosa) type for feeding activity was inversely related to canopy cover. Deer rested most during daytime and night periods. During periods of daylight, deer using the grassland type showed preference for ecotones with certain types offering escape cover. No such preference was observed at night. Deer fed less and rested more when snow depth exceeded 36 cm. No significant differences (P>0.05) in the proportion of time deer devoted to feeding were found in the following comparisons: clear versus cloudy full-moon nights (-50 vs. + 50% cloud cover), full-moon versus new-moon, low versus high wind speeds (0-32 vs. 32-56 km/hr), and warm versus cold temperatures (+18 to -15 vs. -15 to -23 degrees C). No significant relationships were found for the same comparisons in proportion of time devoted to resting.
    • Stocking rate effects on intensive-early stocked Flint Hills bluestem range

      Owensby, C. E.; Cochran, R.; Smith, E. F. (Society for Range Management, 1988-11-01)